1. Field of Invention
This invention relates to apparatus for holding a patient's leg in place during a knee operation, and, more particularly, to apparatus for adjustably holding a foot in place relative to an operating table rail during the installation of a knee joint prosthesis.
2. Description of the Related Art
Before the development of various methods and devices for holding the lower leg and knee during knee surgery, a nurse or assistant typically held the leg in place during an operation. Since such operations were often quite lengthy, the position of the knee was often allowed to vary according to the fatigue of the nurse. Furthermore, the presence of an individual holding the leg and knee often prevented the surgeon from being able to view the operation at a desirable angle and from being able to position himself for best advantage. To overcome these disadvantages, a number of methods and devices for holding the lower leg and knee during knee surgery have been developed.
During prosthetic knee replacement surgery, it is desirable to be able to move the knee to different positions in which it is reliably held still. For example, a prosthesis may be installed with the knee flexed, and subsequently checked in one or more positions with the knee extended, and with adjustments being made as necessary.
Conventional methods for holding the knee of a patient in place on an operating table during knee surgery interpose a wedge-shaped structure below the knee. While this method rigidly holds the knee in place, the subsequent movement of the foot to adjust the position of the knee is precluded as long as the wedge-shaped structure is present to interfere with straightening the leg to lower the knee.
The patent art includes a number of descriptions of devices developed to hold the knee and lower leg during knee surgery. For example, U.S. Pat. No. 3,753,557 describes a device, including a base, adapted to be adjustably and removably secured on a horizontally disposed operating table. An upwardly inclined support supports the leg bent at an angle, preferably less than 45 degrees at the knee, with the knee elevated and with both the upper and lower legs in a substantially vertical plane, being free from obstruction to clear visible and to access to the lateral sides of the knee. The leg is also free from obstruction to lateral movement. The support is also adjustable as to the angle at which the leg may be bent and supported, and to a position in which the leg is supported with the foot elevated to an operating level for foot and ankle surgery. While this device is adjustable to vary the angle at which the leg is bent during surgery, this is variation occurs between the initial angle, preferably less than 45 degrees, to about 90 degrees. What is needed is a device allowing greater variance in the angle at which the leg is held. Furthermore, since all positions of the knee are achieved with the upper part of the leg extending straight upward, some of these positions may leave the knee at an angle which is inconvenient for surgery. What is needed is a device allowing movement of both the upper and lower parts of the leg. Also, what is needed is a device stopping lateral movement of the knee in an adjustable manner.
U.S. Pat. No. 3,802,692 describes apparatus for controlling the attitude of a knee joint, with the apparatus including a housing secured to the center section of an operating table to support the upper part of the leg being operated on. An elongated support for the lower portion of the leg is pivotally mounted on the housing. Reversible drive means, such as a motor controlled by a foot switch pivot the support through a vertical plane to flex and extend the knee joint. Thus, with the upper leg extending horizontally, the knee joint is pivoted between a position in which the lower leg extends horizontally and a position in which the lower leg descends vertically. What is needed is a mechanism providing for extension of the knee beyond this position. Also, since this movement always occurs with the upper leg held horizontally, the knee is not necessarily located in a position convenient for the surgical procedure. Again, what is needed is a device allowing movement of both the upper and lower parts of the leg.
U.S. Pat. No. 4,091,808 describes the use of an interlocking strap to immobilize a leg for knee surgery. The strap is releasably secured around the foot and around the upper leg with the knee flexed. The strap includes an elongate portion of web material having two cooperative strips of fastening material sewn on its opposing major surfaces. The fastening material is curly pile loop and hook-type, self-gripping strip fasteners sold under the trademark VELCRO with the respective hook and loop strips mounted on respective faces of the overlapping strap portions to be fastened together around the parts of the flexed limb. As surgical procedures advance to a point where it is necessary to extend the patient's leg, the strap is removed, or the portion of the strap extending around the upper leg is released and re-fastened to provide a different degree of extension.
U.S. Pat. No. 4,209,012 describes an apparatus for maintaining a patient's knee at a predetermined degree of inflection for a desired time interval. The device includes a foot engaging means, such as a conical foot holder, which is attached to an adjustable strap to engage the patient's thigh and a means for fixing the strap length once it has been adjusted. The adjustable strap includes an inner loop which extends around the patient's thigh, and an outer loop, which is clamped together to establish the length of the inner loop, and thereby to establish the degree of inflection of the knee. This length adjustment is varied as required during a surgical operation.
While the devices of U.S. Pat. Nos. 4,091,808 and 4,209,012 provide a means for establishing and adjusting the degree of inflection of the patient's knee, a provision is not made for controlling lateral movement of the knee. The leg is free to rotate laterally at the hip, with only a distance between the ankle and the thigh where the strap is attached being held. The rotation of the leg may be accompanied by movement of the foot. What is needed is a way to prevent such rotation of the hip and movement of the foot.
U.S. Pat. Nos. 5,007,912 and 5,514,143 describe apparatus for positioning the femur and tibia of a leg during prosthetic knee surgery. Each of these devices includes a femoral section fixedly mounted on the femur and a tibial section fixedly mounted on the tibia, together with a mechanism extending between the femoral and tibial sections to control their relative movement. While precise positioning and movement of the bones are achieved in this way, these advantages are obtained at the expense or requiring elaborate mechanisms and frameworks adjacent the knee and leg. What is needed is a way for holding the knee in a variety of positions without requiring the positioning of mechanical devices immediately adjacent the knee, so that access to the knee during the surgical procedures is not impeded.
Several U.S. patents describe devices for holding the leg during arthroscopic knee surgery without addressing the question of supporting the lower leg in a manner allowing variation in the position of the knee, since the type of movement advantageously applied during prosthetic knee surgery is not needed during arthroscopic knee surgery. For example, U.S. Pat. Nos. 4,549,540 and 4,457,302 describe devices for immobilizing the patient's thigh during arthroscopic knee surgery without addressing the question of holding or supporting the lower leg. U.S. Pat. No. 4,407,277 describes apparatus for holding the leg straight and for applying various torques and axial forces to the knee.